United traces its roots to Varney Air Lines (VAL), which Walter Varney founded in 1926 in Boise, Idaho. Continental Airlines is the successor to Speed Lanes, which Varney had founded by 1932 and whose name changed to Varney Speed Lines in 1934. VAL flew the first privately contracted air mail flight in the U.S. on April 6, 1926.
In 1927, William Boeing founded Boeing Air Transport to operate air mail routes under contract with the United States Post Office Department. In 1929, Boeing merged his company with Pratt & Whitney to form the United Aircraft and Transport Corporation (UATC) which then set about buying, in the space of just 28 months, Pacific Air Transport, Stout Air Services, VAL, and National Air Transport, as well as numerous equipment manufacturers at the same time. On March 28, 1931, UATC formed United Air Lines, Inc. as a holding company for its airline subsidiaries.
In late 2006, Continental Airlines and United had preliminary merger discussions. On April 16, 2010, those discussions resumed. The board of directors of Continental and UAL Corporation agreed on May 2, 2010, to combine operations, contingent upon shareholder and regulatory approval. On October 1, 2010, the UAL Corporation changed its name to United Continental Holdings, Inc. The carriers planned to begin merging their operations in 2011. The merged airline began operating under a single air operator's certificate from the Federal Aviation Administration on November 30, 2011. On March 3, 2012, United and Continental merged their passenger service systems, frequent-flier programs, and websites, which virtually eliminated the Continental brand with the exception of its logo. On Thursday June 27, 2019, the parent company's name changed from United Continental Holdings to United Airlines Holdings.